Tetrachloro fluorotoluene



Oct. 31, 1944. B -s BlGGs 2,361,590

TETRACHLORO FLUOROTQLUENE Filed Dec. 6, 1938 FIG. lY

l/ PAPER INPREGNATED 'lv/TH A TETRAcHLoRoFLuoRoroLun/E FIG.2

/4 A TETRAcHLonoFLuonarou/ENE /4 A TETRACHLROFLUOROTGLUENE /N VEN TOR ATTORNEY Patented Oct. 3l, 1944 UNITED STATES PATENT OFFICE 2,361,590 'raraAcnLoao FLUoao'roLUENE Barnard S. Biggs, Summit, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation oi' New York 5 Claims.

condensers are used in relatively large numbersl and any reduction in their size without appreciable diminution in their functional characteristics results in material economies.

An object of this invention. is to reduce substantially the size of apparatus employed in electrical systems.

Another object is to utilize in electrical apparatus materials having high dielectric constants and desirable physical and electrical properties.

In accordance withI this invention tetrachloro iluorotoluenes are employed as dielectric materials for use in electrical apparatus, such as condensers. They are solids under temperate conditions to which condensers are ordinarily subjected. They have high dielectric constants and retain these high dielectric constants at high frequencies and at unusually low temperatures. They are non-hygroscopic, are chemically stable, do not undergo electrolytic changes, and do not decompose or break down under conditions of use in electrical apparatus. Further, the tetrachloro iluorotoluenes may be employed with other dielectrics which possess molecular rotation in the solid state as disclosed in W. A. Yager Patent 2,319,838, issued May 25, 1943, and in the cependappllcation of B. S. Biggs, S. O. Morgan and A. H. White, Serial No. 244,171, filed December 6, 1938. The tetrachloro fluorotoluenes are tetrachloro ortho-fluorotoluene, tetrachloro meta-uorotoluene and tetrachloro para-uorotoluene.

The tetrachloro iiuorotoluenes are best prepared by chlorinating their respective iluorotoluenes. For example, tetrachloro meta-iluorctol.

'uene is produced by chlorinating meta-fluorotoluene. This chlorination proceeds less rapidly than the chlorination of toluene itself. But by the use of iron powder or antimony pentachloride or both as catalysts in carbon tetrachloride solution chlorination to the level of four chlorine atoms may be obtained. The resulting product is fractionally distilled and the desired material obtained in the fraction boiling at about 269 decrees C. It is further purified by crystallization from a solvent, such as benzene or cyclohexane. It crystallizes in white needles, melting at 146 degrees C. The dielectric constant of tetrachloro iiuorotoluene is 5.8 at 20 C.

Another method of preparing the tetrachloro iluorotoluenes is to nitrate the appropriate tetrachloro toluene, reduce the nitro group to the amino group, replace the amino group with a iiuorine atom either by diazotizing in the presence of hydrofluoric acid or pyrolysls of the diazonium borouoride.

Tetrachloro ortho-iluorotoluene, tetrachloro meta-iluorotoluene or tetrachloro paraiiuoro toluene may be employed either alone or together with another dielectric in electrical apparatus, as dielectric guides as shown in.U. S. Patent 2,129,- 7 11, granted to G. C. Southworth on September 1.3, 1938. y

The manner of utilizing a tetrachloro fluorotoluene in condensers is shown in the accompanying drawing in which:

Fig. 1 is a. perspective view of a condenser in which the dielectric is a tetrachloro iiuorotoluene; and

Figs. 2 and 3 are cross-sectional views of capacitances including a tetrachloro iiuorotoluene as the dielectric.

In Fig. 1 sheets of a porous dielectric llfsuch as paper, areV impregnated with a tetrachloro nuorotoluene such as tetrachloro meta-fluorotoluene. interposed between the sheets of the dielectric are a pair of conducting sheets l0. Both the dielectric and foils are wound in a well-known manner to form a roll type condenser. Two metallic strips I2 are electrically connected to the electrodes i0 to form the-terminals of the condenser. Alternately the tetrachloro fluorotoluene may be applied as a coating Il on a metal foil I6 as shown in Figs. 2 and 3. A strip of another dielectric li may be positioned between the coating H as shown in Fig. 2 and the coated foils piled alternately in a. well-known manner to form a condenser.

What is claimed is:

1. A tetrachlorotluorotoluene.

2. Tetrachloro-ortho-iluorotoluene.

3. Tetrachloro-meta-nuorotoluene.

4. Tetrachloropara-fluorotoluene.

5. The method of preparing a tetrachlorofluorotoluene which comprises chlorinating a monofluorotoluene in the presence of antimony pentachloride as a-catalyst until a tetrachlorouorotoluene is formed.

BURNARD S. BIGGS. 

